Vacuum cleaners which utilise cyclonic separators are known. In a typical cyclonic vacuum cleaner, an airflow in which dirt and dust is entrained enters a first cyclonic separator via a tangential inlet which causes the airflow to follow a spiral or helical path within a collecting chamber. Centrifugal forces act on the entrained dirt to separate the dirt from the flow. Relatively clean air passes out of the chamber whilst the separated dirt and dust is collected therein. In some appliances, the airflow is then passed to a second cyclonic separator stage which is capable of separating finer dirt and dust than the first cyclonic separator. An example of such an arrangement is shown in EP1268076, in which a plurality of cyclones work in parallel within the cyclonic separator. Each individual cyclone is small in comparison to that used in an equivalent single cyclone apparatus. The relatively small size of each individual cyclone has the effect of increasing the centrifugal force acting on particles entrained in the airflow passing through the cyclone body. This increase in the force results in an increase in the separation efficiency of the apparatus. The fine dirt and dust separated by the second cyclonic separator stage is typically also collected in the collecting chamber. The cleaned airflow then exits the collecting chamber.
In domestic vacuum cleaner applications, it is desirable for the appliance to be made as compact as possible without compromising the performance of the appliance. It is also desirable for the efficiency of the separation apparatus contained within the appliance to be as efficient as possible and to separate a high proportion of very fine dust particles from the airflow. A further consideration is that the separation apparatus be simple to manufacture and assemble.
The invention provides cyclonic separating apparatus having a longitudinal axis and comprising an upstream cyclonic separator and a downstream cyclone assembly comprising a plurality of cyclones arranged in parallel with one another in first and second sets, at least some of the cyclones of the first set having a longitudinal axis inclined at a first angle to the longitudinal axis of the cyclonic separating apparatus, and at least some of the cyclones of the second set having a longitudinal axis inclined at a second angle to the longitudinal axis of the cyclonic separating apparatus, the second angle being greater than the first angle.
The arrangement of the invention makes use of the high separation efficiency achievable by a plurality of parallel cyclones whilst also allowing the downstream cyclone assembly to be compactly packaged. The downstream cyclone assembly of the invention occupies a smaller volume than it would if the downstream cyclones were formed with their longitudinal axes substantially parallel. This allows the apparatus to be utilised in an appliance such as a domestic vacuum cleaner.
Preferably, all of the cyclones of the first set have a longitudinal axis inclined at the first angle to the longitudinal axis of the cyclonic separating apparatus. It is also preferable that all of the cyclones of the second set have a longitudinal axis inclined at the second angle to the longitudinal axis of the cyclonic separating apparatus. Such an arrangement makes the cyclonic separating apparatus easy to manufacture and assemble.
Advantageously, the cyclones of the second set at least partially surround the cyclones of the first set, which provides a compact configuration of the downstream cyclone assembly.
Advantageously, at least some of the cyclones of the downstream cyclone assembly have a cap inside the respective cyclone, the cap comprising an inlet to the cyclone. By locating the inlet to the cyclone within the cyclone itself, a more compact arrangement can be made.
Preferably, the cap is a one-piece construction that also includes at least some of the following: a helical channel extending from the inlet to the interior of the cyclone; an outlet for the cyclone; one or more baffles arranged to reduce turbulence in the outgoing airflow. Such a one-piece construction further simplifies manufacture and assembly of the cyclonic separator.
The helical channel can extend in either a first rotational direction (e.g. clockwise) or in the opposite rotational direction (anti-clockwise). Colour coding may be employed so that the assembly line operator can differentiate between caps having a clockwise channel from those having an anticlockwise channel.
The invention further provides a method of manufacturing cyclonic separating apparatus having a longitudinal axis, and a downstream cyclone assembly comprising a plurality of cyclones arranged in parallel with one another, the method comprising; moulding a first component comprising a first set of cyclones, at least some of which have a longitudinal axis inclined at a first angle to the longitudinal axis of the assembled cyclonic separating apparatus; and moulding a second component comprising a second set of cyclones, at least some of which have a longitudinal axis inclined at a second angle to the longitudinal axis of the assembled cyclonic separating apparatus, the second angle being greater than the first angle.
The method of the invention allows a more complex downstream cyclone assembly to be manufactured than was possible hitherto, making it possible for a more compact arrangement to be achieved.
The invention will now be described, by way of example, with reference to the accompanying drawings, in which: